1. Field of the Invention
The present invention relates to a dyeing assistant for use in printing colors on cloths made of hydrophobic fibers. More particularly, the present invention relates to a dyeing assistant for printing of hydrophobic fibers which makes it possible to obtain uniform deep color printing of hydrophobic fiber cloths, sharp printing of complicated fine designs, efficient printing operation, maintenance of a soft feel after heat-treatment of the printed cloth and a sufficient dimensional stability of the cloth.
2. Description of the Prior Art
Knitted goods and textiles made of hydrophobic fibers, such as polyesters and triacetates, have heretofore been printed by applying to the fabric a printing paste containing a water-soluble thickener, a dye, an acid for pH regulation and a reduction-preventing agent, subjecting the thus-treated fabric to an intermediate drying treatment and then steaming the same with high pressure saturated steam at 120.degree.-140.degree. C. for 20-40 minutes to fix the dye.
However, recently, steaming has been effected using super-heated steam under atmospheric pressure or continuous fixing has been effected by the dry heat thermosol method in many cases for labor saving purposes.
The printing process wherein fixing is effected by the superheated steaming method (HTS method) or the dry heat thermosol method has a serious defect that if a conventional printing paste is used, the build-up rate of the dye is inferior to that obtained by the high pressure steam fixing process.
There have been numerous studies and patents relating to the elimination of said defect, i.e. to achieve an improvement in the build-up rate. For example, it is disclosed that ethylene oxide adducts of vegetable oils, etc. are suitable for this purpose in "American Dyestuff Reporter" May 25, 1964, (lines 5-14, the last column, page 419) and the same journal, July 19, 1965 (lines 17-3 from below, the last column, page 547). There have been published numerous patents related to those techniques. For example, in Japanese Patent Publications Nos. 8428/1967 and 8429/1967, polyhydric alcohol esters and ethylene oxide adducts of aromatic phenols are disclosed. However, by those techniques, level dyeing cannot be attained, because the fixing temperature is very high. In Japanese Patent Publication No. 38755/1970, ethylene oxide adducts of alkylamides are disclosed. In Japanese Patent Publication No. 30034/1969, phosphorus compounds are disclosed for use on acrylic fibers and polyamide fibers. In Japanese Patent Publication No. 8968/1971, a combination of a polyacrylic acid alkylene glycol ester and an alkoxylated compound prepared from phenol, formaldehyde and an amine by the Mannich reaction is disclosed. In Japanese Patent Publication No. 11473/1971, it is described that urea or ethylene urea is preferred for this purpose.
Particularly, the inventions disclosed in Japanese Patent Laid-Opens Nos. 29066/1972, 39776/1973, 66974/1974, 66975/1974, 72480/1974 and 90783/1975 relate to improving the build-up rate. Recently, the use of high molecular polyamine compounds as color development promotors has been proposed in Japanese Patent Laid-Opens Nos. 154584/1975, 1774/1976 and 19874/1976. Further, the joint use of a fatty acid glyceride and an ester of fatty acid and polyoxyethylene has been proposed in Japanese Patent Publication No. 1038/1977.
Although many ideas have been proposed, as described above, the fixing by the superheated steaming method or thermosol method has not been completely satisfactory yet for the reasons which will be described below.
As representative substances used for increasing the fixing rate, there have been used castor oil, ethylene oxide adducts of castor oil and sorbitan fatty acid esters. By using those substances, polyester and triacetate textiles can be printed continuously and the labor required for the HTS or thermosol fixing treatment in the printing process can be reduced. A dyeing deepness equivalent to or superior to that obtained by high pressure steaming in the batch system can be obtained and printed cloths having a substantially level hue in the range of from light to dark colors can be obtained. However, the above substances have still the following three disadvantages:
(1) There occurs a rubbing-off phenomenon whereby the dye is separated from the cloth in an intermediate drying step (i.e. a phenomenon in which the dye, before the fixing, is transferred to another portion of the cloth whereby to spoil the design).
(2) The feel of the cloth becomes rough and stiff after the application, drying and fixing steps due to the high temperature fixing step. This defect cannot be eliminated by desizing the cloth.
(3) In case of a design wherein a non-dyed white background is left, during the heat fixing step the rate of temperature elevation in the portions to which a printing paste has been applied differs from that in the portions to which the printing paste has not been applied and, therefore, a difference in textile elongation is caused which creases or wrinkles the cloth partially. The wrinkles cannot be eliminated easily by heat setting. This phenomenon is particularly remarkable in thin textiles such as voile and Georgette crepe.
For overcoming those defects, an idea has been proposed wherein an emulsion, dispersion or a solution of a combination of a fatty acid glyceride with a long chain aliphatic alcohol, an alkylphenol or a fatty acid/ethylene oxide adduct is used for improving the fixing in the printing. However, the dye agglutinates in the printing paste to cause specking in the printed products. If a polyoxyethylene glycol or polyoxyethylene alkyl ether is used as an emulsifying component, so-called "bleeding" is caused which makes clear printing impossible.
It has been reported further that if a fatty acid glyceride is added to the printing paste together with a fatty acid ester of polyoxyethylene glycol, the dye specking can be prevented whereby to obtain a dyed product of a level, deep color having a sufficiently sharp design.
However, all of the above described three defects could not be overcome by the conventional techniques.
After intensive investigations for the purpose of overcoming said defects, the inventors have discovered an excellent dyeing assistant useful in the printing of designs on cloths made of hydrophobic fibers. The present invention has been completed on the basis of this discovery.